Investigations of the cycloadditions of the ketene-sulfur dioxide adduct showed that it reacted easily and rapidly with fluorenylideneaniline. The adduct did not react with benzaldehyde and benzophenone hydrazones nor with 2-aminobenzimidazoles. Some substituted 2-(phenylsulfinamoyl)acetanilides were prepared by a new route and will be oxidized to the corresponding sulfonamides. Phenyl isocyanate appears to react with sulfur dioxide to give an adduct which can be trapped by benzylideneaniline to give a novel six-membered heterocycle. Rigorous proof of structure for this compound has not as yet been completed. Further work is in progress to explore the applications of this reaction and characterize the intermediate adduct.